Current fuel injectors have valve opening pressures (VOP) for the needle check that are limited by the size of the coil spring capable of fitting within available space in the injector. In most fuel injection applications, higher valve opening pressures provide numerous benefits, including cleaner engine emissions, lower injector minimum delivery capability and more efficient combustion. The current state of the art in fuel injector needle check valves is to utilize a coil spring as the biasing element. Unfortunately, coil springs cannot always provide the sufficient biasing force in applications requiring a high valve opening pressures, and the option of using larger coil springs is not available due to space constraints. Some manufacturers have experimented with substituting stacks of belville washers in place of conventional coil biasing springs; however, the force constant of the belville stack is not reliably predictable and tends to change over time. What is needed is a biasing spring with a reliably predictable force constant that will fit in roughly the same volume of the current coil springs, yet provide a relatively large force constant, and perform predictable over a working life comparable to prior art coil springs.